A communication network includes a plurality of relay devices in order to carry out communication between terminal devices. For example, in the 3GPP (3rd Generation Partnership Project) for laying down standard specifications for mobile communication networks, they are examining a network configuration in which user traffic and control traffic are relayed by using node devices such as MMEs (Mobility Management Entities), SGWs (Serving Gateways), and PGWs (Packet Data Network Gateways).
In recent years, it has been examined to efficiently use resources of a network by virtualizing node devices forming the network. For example, a case where a node device uses a VM (Virtual Machine) for each interface through which the node device connects with another node device is explained hereinafter. When traffic between the node device and the other node device increases, a VM for performing communication with the other node device is added in the node device. Further, when the traffic between the node device and the other node device decreases, a VM for performing communication with the other node device is deleted and the deleted VM may be added (i.e., reused) as a VM that used for performing communication with another node device. The VM may be, for example, a communication resource, such as an internal memory, disposed inside the node device. Further, the VM is used as a partial element for forming the node device. That is, the above-described example is based on the precondition that a plurality of interfaces are used as partial elements in the node device and the VM corresponds to a communication resource constituting one of the interfaces.
In this way, by adding or deleting a VM according to the amount of traffic processed by the node device or according to other conditions, the communication resources in the network can be efficiently used. In Non-patent Literature 1, virtualization in a network or in a node device is specified as NFV (Network Functions Virtualization).
Note that examples of the main factor for adding a VM in a node device include a case where there is a possibility of the occurrence of congestion in the node device or in the whole network due to an increase in traffic or the like. When there is a possibility of the occurrence of congestion, the increase in traffic can be handled by adding a VM. For example, in the case where a mobile communication network is taken into consideration, traffic that is transmitted from a terminal device due to the occurrence of an event such as an ATTACH in which upon power-on of the terminal device, the terminal device connects to the mobile communication network or a handover that occurs as the terminal device moves flows into a newly-added VM.
On the other hand, examples of the main factor for deleting a VM in a node device include a purpose of preventing wasteful use of communication resources when the processing capacity of the node device considerably surpasses the traffic capacity thereof. That is, it is possible to reduce the power consumption and reduce the communication resources by eliminating electric power supplied to a VM that has been excessively (or wastefully) used.